/*
 * Copyright 2020-2024 Typelevel
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cats.effect.unsafe.metrics

import scala.concurrent.duration._

sealed trait CpuStarvationMetrics {

  /**
   * Returns the current number of times CPU starvation has occurred.
   *
   * @note
   *   the value may differ between invocations
   */
  def starvationCount(): Long

  /**
   * Returns the current (last) observed clock drift.
   *
   * @note
   *   the value may differ between invocations
   */
  def clockDriftCurrent(): FiniteDuration

  /**
   * Returns the maximum clock drift observed since the launch.
   *
   * @note
   *   the value may differ between invocations
   */
  def clockDriftMax(): FiniteDuration
}

object CpuStarvationMetrics {

  private[metrics] def apply(sampler: CpuStarvationSampler): CpuStarvationMetrics =
    new CpuStarvationMetrics {
      def starvationCount(): Long =
        sampler.cpuStarvationCount()

      def clockDriftCurrent(): FiniteDuration =
        sampler.clockDriftCurrentMs().millis

      def clockDriftMax(): FiniteDuration =
        sampler.clockDriftMaxMs().millis
    }

}
